This Tuesday, November 15, planet Earth officially has more than 8 billion human beings, according to the United Nations estimate. This represents an eightfold increase in the number of inhabitants compared to 1800. Gilles Pison, professor emeritus at the National Museum of Natural History (MNHN), adviser to the management of the National Institute for Demographic Studies (INED) and author of the’World Population Atlas (Ed. Otherwise) returns for L’Express to the drivers of this tremendous expansion, and the challenges it entails for the planet.
L’Express: Let’s start by removing some doubts. Are we really sure to have crossed the threshold of 8 billion human beings?
Gilles Pison: It’s true, it’s quite amazing that we know how big we are on a planetary scale. However, we have censuses for all countries and all regions of the world. Which was not the case a few decades ago.
It is on the basis of this work that the United Nations provides an estimate of the population at the global level. Of course, the quality of censuses varies. Sometimes the numbers have to be corrected when we are faced with a clear understatement or overstatement. We consider that there is an uncertainty of 1 or 2% on the final result. It is therefore possible that we already crossed the threshold of 8 billion two years ago. We could also cross it in two years. That said, demographic trends are well known. This announcement, like the United Nations projections for 2050, are relatively solid.
How high will the population grow?
We were one billion in 1800, we are 8 billion today and we should be two billion more by 2080 according to United Nations projections. However, this moment should be seen as a peak. The world population continues to increase but at a decelerating rate and this for 60 years. The annual growth rate reached its maximum (over 2%) in the 1960s. Today, it is around 1%. It must be said that fertility continues to decline. Today women give birth to an average of 2.3 children. It was more than double 50 years ago.
In their projections, the United Nations assumes that the trend will continue. Thus, the maximum of the population would be reached by 2100 – we would then be 10.4 billion inhabitants. At this horizon, China would have almost half as many inhabitants as today (1.4 billion inhabitants). Europe as a whole would see its population stay at about the same level or drop slightly from today.
Are these figures the subject of a consensus?
The future is not written. Imagine an asteroid similar to the one that fell 66 million years ago contributing to the fifth mass extinction of species and the disappearance of the dinosaurs, crashing into our planet. This would render all forecast scenarios invalid. As well as the arrival of a new pandemic with an extremely nasty germ.
Fortunately, these events that cannot be anticipated are also very unlikely. In the current state of knowledge, it is therefore better to stick to the United Nations projections. People like to scare themselves. But we have to realize that changing demographic trends is not easy. Even the Covid epidemic has not succeeded. It led to an excess mortality of 15 million people, compared to what was expected during the years 2020 and 2021. But the population has not fallen for all that: currently there are twice as many births as deaths and the world population increases by almost 80 million people every year! So in 2020-2021 the increase was simply a little lower.
The anxiety vis-à-vis global warming, which pushes some young people of the new generations not to want children, is it not likely to weigh heavily on demographic forecasts?
In our discipline, 10, 20 or 30-year forecasts are relatively reliable due to demographic inertia. Even if world fertility fell to one and a half children per woman everywhere on the planet and immediately (this is the level of Europe) the world population would continue to increase for a few decades because it includes a large proportion of young people adults of childbearing age. Even if each of them does not have many children, this still translates into a high number of births. Moreover, deaths remain low on a global scale because we have a small proportion of humanity that is old, even very old. In summary, we will not escape an increase of 2 billion humans by 2080 due to the demographic inertia that no one can prevent.
How can these two billion additional inhabitants be integrated into an environment already battered by climate change?
The real question, the one on which the survival of the human species depends, is less that of the number of people on Earth than that of their lifestyles. From today, it is possible to act on them in order to make them more respectful of the environment, of biodiversity, and more economical in resources. It is true, part of the youth is anxious at the idea of having children. Especially since they represent a financial cost. But to those who decide to take the plunge, I say: have as many children as you wish. Simply, make sure they have sustainable lifestyles.
These children will be 25 or 30 years old in 2050. If at that time their way of life remains too close to ours, if they emit as many greenhouse gases as we do, then we will be in a situation impossible to to manage. From this point of view, the inhabitants of the countries of the North have an important role to play since their ways of life are, so to speak, copied by the populations of the countries of the South. If we adopt lifestyles that are more respectful of the environment, this will have a multiplier effect since the countries of the South will certainly also adopt sustainable lifestyles.
Will feeding the planet be much more difficult with 10 billion inhabitants?
When I read the work of my colleagues, I conclude that the planet must be able to feed 10 billion people better than it does for 8 billion. Today, part of humanity does not eat enough in quantity or quality. Another part eats too much and badly. We see that our diets are not sustainable.
In particular, we will have to reduce our meat consumption. The land we cultivate and the food we import from it are used in part to feed our livestock, which we then eat. This is a major source of waste. Developing our agriculture is a challenge. But it seems to be within reach.